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Changing oil in the gearbox

In most cases, caring about your car is a recipe for its long, failure-free operation. Every driver should remember at least about regular checks and replacement of operating fluids and elements which wear out in daily driving.

The most essential thing to do is, of course, to change oil. For many drivers, this solely means engine oil. This is quite an oversight as it is equally important to change oil in the gearbox.

Myths about changing oil in the gearbox

A seized engine is the most common result of negligence connected with old oil. When you do not follow the manufacturer’s recommendations and forget about changing oil, an engine failure may be a very costly problem. The drivers who are not car enthusiasts, but rather treat their cars as a tool, are seldom aware of the need to change oil in the gearbox. Believing in car superstitions, some people claim that it is an unnecessary expense. Many drivers think that changing oil in the gearbox is a must only in cars used in very harsh conditions, e.g. taxis, ambulances, or police cars.

Why change oil in the gearbox?

Oil in the gearbox fulfils many functions. Not only does it lubricate the individual elements to substantially reduce friction, but also cools the heated subassemblies as well as mitigates and attenuates gear strokes. In addition, it reduces vibrations, protects against corrosion, and keeps everything clean. Oil should have the right parameters, adjusted to a specific car. Different types will be used for a gearbox in a city car and a sports car or light commercial vehicle, where the load is higher. Oil must not froth or aggressively affect gaskets and other non-metal elements. It should also maintain proper consistency and lubricating properties regardless of temperature.

Technology advancements in gearbox oils

It would seem that oils from ten years ago are the same as today. Nothing could be more wrong. At first glance, the liquid from years ago may look the same as the one we can now find on store shelves, but the devil is in the details. Or more specifically, in the production technology.

In recent years we have witnessed very fast development of transmission technologies. Gearboxes will have to keep up with propulsion units, which are increasingly smaller and stronger. A modern 1.6 litre compression-ignition engine generates the same power and torque as a few times bigger engine of a truck from a few years ago. Today’s gearboxes need to handle the same forces with incomparably smaller dimensions. Smaller dimensions also mean that loads are concentrated on a smaller surface. All this means that the transmission (automatic or manual) must handle very large loads, which requires superior lubrication.

All this would make the oil from previous years, which did not have to “fight” against such harsh conditions, unable to cope in a modern gearbox. Therefore, manufacturers had to develop new formulas, which would be able to keep the transmission fully operational for thousands of kilometres. Nothing lasts forever, though. This is why changing oil in the gearbox is so important.

First signs of worn-out oil in the gearbox

As we become aware of the need to change oil in the gearbox, an obvious question arises: when to do it? When we notice first signs of oil wear, it is usually too late to avoid a costly repair. For this reason, it is better to change oil in advance rather than too late. This will help us avoid future expenses. In many cases, the mileage of 50 thousand kilometres seems the right moment, although a lot depends on use patterns and the car’s age etc.

After some time, even top quality oil will lose its properties. It ages rather slowly, but gradually and systematically. If you are using manual transmission in which each gear change involves a noise or a grind, it signals oil wear and a damaged gearbox. For automatic transmission, each change of gear with worn-out oil involves a jerk and resistance. Some other strange sounds may also appear.

Changing oil in automatic transmission

Car manufacturers declare that the oil poured into the gearbox in the factory should be enough for the car’s entire lifecycle. As this is somewhat ironic, we can respond in the same fashion: yes, but only if the lifecycle is 150 thousand kilometres. We do not know if car manufacturers assume such short durability of their cars or they wilfully mislead their customers to profit from repairs. Many independent experts and property appraisers claim that the optimum mileage after which you should change oil in automatic transmission is ca. 60-100 thousand kilometres. Subsequent changes should be made more often, i.e. after 40-60 thousand kilometres. The older the car, the more frequent the change, i.e. even every 30-40 thousand kilometres. Ok, but what does the process itself look like?

Unfortunately, oil change in automatic transmission is not easy, which makes the whole process rather costly. Still, the cost will be lower than in case of repair or replacement of a broken automatic transmission. In most cases, modern automatic transmissions are designed in such a way that in order to change the entire oil, you need to disassemble them completely, almost down to their bits and pieces.

Entrust oil change in automatic transmission to professionals

Doing it without due care may result in leaving some old oil in the car’s nooks and crannies. In turn, this accelerates the wear of the new oil. This is why it is worth entrusting the task to a mechanic who specialises in such repairs. While you can decide to use a half-measure, i.e. change around 60 percent of oil for new one (the rest stays in the main), remember that the next change will have to be made much sooner.

For a professional mechanic, it will be enough just to look at the colour and consistency of the worn-out oil to assess the transmission’s condition. Sometimes a coolant gets to the gearbox oil through worn-out gaskets, which dramatically reduces its durability and affects properties. It is also worth checking the oil filter for the presence of fillings – it should be a very disturbing signal suggesting considerable gearbox wear.

For automatic transmission, wrong oil may cause a serious failure or, in extreme cases, a serious failure of the gearbox. Unfortunately, choosing the right oil is very difficult. Sometimes a given manufacturer uses different varieties in the same model, which, what is worse, are available only in authorised repair shops. For this reason, before you visit a repair shop, you should try to learn exactly what oil there is in your car’s gearbox.

Changing oil in manual transmission

For manual transmission, the whole process is much simpler, whereas negligence in this respect has much less severe consequences. First of all, inside the body there are strong magnets, which capture the metal fillings created during use. Moreover, changing the worn-out oil does not involve disassembling the entire gearbox. For this reason, the whole process is not as complicated as in the case of automatic transmission. Still, you need to be careful as there is no fit-for-all oil. Although typically API GL-4 and GL-5 oil classes are used, there are also exceptions, which work with engine oils. If you have doubts, check it with a specialist repair shop.

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